Arrangement and method for the generation of water on board an aircraft

ABSTRACT

An arrangement and a method are proposed for the generation of water on board an aircraft with the use of one or more fuel cells, whereby low-temperature fuel cells are provided as fuel cells. 
     It is proposed that several single-cell or few-cell fuel cells may form a fuel-cell panel or cell array and several cell panels or cell arrays may be arranged close to the inside of the aircraft fuselage and the cathode side of the at least one fuel cell has a chamber pointing to the exterior of the aircraft for the condensation of the water contained in the air and the anode side has a chamber carrying a combustion gas, for example hydrogen. 
     With the proposed solution, a reduction in the storage capacity for drinking water and its quality-assured provision may be enabled and moreover, with the use of fuel cells as a virtual power station, the energy demand on engine generators, auxiliary power unit (APU) or ram air turbine (RAT) may be reduced.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. patent application Ser. No. 10/999,052,filed Nov. 29, 2004 now U.S. Pat. No. 7,108,229 in the name of ClausHoffjann et al. and entitled ARRANGEMENT AND METHOD FOR THE GENERATIONOF WATER ON BOARD AN AIRCRAFT, which claims priority of GermanApplication No. 103 56 012.2-45, filed Nov. 27, 2003.

FIELD OF THE INVENTION

The invention relates to an arrangement and a method for the generationof water on board an aircraft with the use of one or more fuel cells,whereby low-temperature fuel cells are provided as fuel cells.

TECHNOLOGICAL BACKGROUND

A power supply unit on board an aircraft as a substitute for a mainengine, an auxiliary power unit, a ram air turbine or an NiCd battery isknown from EP 957 026 A2. A fuel cell serves here to generate directcurrent, whereby used air from the aircraft air-conditioning unit oraircraft external air is used for the air supply to the fuel cells.Water for the water supply on the aircraft is obtained from the fuelcell exit air, whereby the fuel cell exit air is then carried away tothe aircraft surroundings, which also applies to the hydrogen emergingfrom the fuel cell. Generation of water by means of a water condenserarranged in the exit air flow can take place as an advantageoussecondary effect. The arrangement of the fuel cell module is provided inthe aircraft tail.

SUMMARY OF THE INVENTION

There may be a desire to provide an arrangement and a method, wherein atleast one fuel cell is provided for water generation and for currentgeneration, which is integrated in a favourable manner into thepassenger cabin area of an aircraft in a space-saving way.

In an arrangement according to an exemplary embodiment of the invention,several single-cell or few-cell fuel cells form a fuel-cell panel orcell array and several cell panels or cell arrays are arranged close tothe inside of the fuselage skin and the cathode side of the at least onefuel cell has a chamber pointing towards the exterior of the aircraftfor the condensation of the water contained in the air and the anodeside has a chamber carrying a combustion gas, for example hydrogen.

There may be an advantage that, with the proposed solution, a reductionof storage capacity for drinking water and its quality-assured provisionis enabled and moreover, with the use of the fuel cells as a virtualpower station, the energy requirement on engine generators, auxiliarypower unit (APU) or ram air turbine (RAT) can be reduced or completelysaved. The generation of water may be of particular importance forapplication in aviation and space travel, because here autonomoussystems are required for the onboard supply in order to avoid largestorage volumes and weights for the required drinking water. A modularconcept consisting of numerous identical components stands to the fore,which, with a high degree of redundancy, solves the aspects of power andwater supply on board aircraft by means of a fuel and air supply,likewise having a modular construction, as well as water condensationand distribution.

Examples of embodiment of the invention are shown in the drawing, whichare described in greater detail below with the aid of FIGS. 1 to 4.Identical components are designated by identical reference numbers inthe figures.

In detail, the figures show the following:

FIG. 1 a partial cross-section of an aircraft with a diagrammaticallyrepresented arrangement of a fuel-cell panel according to the invention,

FIG. 2 a diagrammatic representation of an arrangement of fuel-cellpanels in a view from in front,

FIG. 3 a form of embodiment, according to the invention, of anarrangement for the generation of water in the area of the passengercabin and

FIG. 4 a sectional representation of a fuel-cell panel in the stateinstalled in a passenger cabin of an aircraft.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Fuel cells can also be used for water generation, apart from currentgeneration. The arrangement described below serves to reduce storagecapacity for drinking water and its quality-assured provision and alsoas a virtual power station, which reduces or completely saves the energydemand on engine generators, auxiliary power unit (APU) or ram airturbine (RAT).

FIG. 1 shows a partial cross-section of an aircraft 100 with adiagrammatically represented arrangement of a fuel-cell panel 1according to the invention. Panel 1 is provided in the vicinity offuselage outer skin 10 of aircraft 100.

Panel 1 can be mounted directly on the cabin structure or on aircraftstructural parts, such as on rib 11 of an aircraft (see also FIG. 4,suspension 9). Several of these panels form a cell matrix 22 (see forexample the form of embodiment in FIG. 3). Panel 1 is flexible andcurved in such a way that it conforms to the inside of the cabin orinside of fuselage skin 10, whereby the cathode side points outwardstowards the fuselage skin and the anode side towards the interior of thecabin space.

Each panel forms a self-contained and completely encapsulated systemwhich prevents the media being supplied and carried away from beingreleased to the passenger cabin or outside the aircraft. It can be seenin connection with FIG. 2 that the required media are supplied by meansof piping systems, such as a combustion gas supply 18, for example ahydrogen/H₂ supply, and an atmospheric oxygen supply 15, which isobtained from the cabin air, and consumed media are carried away bymeans of a condensate discharge 17 and an exit-air and residual-gasdischarge 16.

Air supply 15 and exit-air and residual-gas discharge 16 are arrangedabove panel 1, preferably in the roof area of aircraft 100. Combustiongas supply (H₂ supply) 18 and discharge 17 of the generated water arerouted via piping systems from below to panel 1 and are preferablyprovided close to aircraft floor 19 in the area of outer skin 10.

It can be seen from FIGS. 2 and 3 that, in the present form ofembodiment, fuel-cell panels 1, 1′, 1″ may be distributed uniformly onthe inside of outer skin 10 for the purpose of optimising the weightdistribution.

It is shown in FIG. 3 that a large number of fuel cells (individual cell21 or multiple-cell elements) can be assembled into cell arrays 20A,20A′, 20A″ . . . along outer skin 10 of aircraft 100. These cell arrays20A, 20A′, 20A″, 20B, 20B′, 20B″, 20C, 20C′, 20C″ . . . form a cellmatrix 22, which can be arranged for example along the whole cabin areaon fuselage outer skin 10, whereby only an area between cutouts 10A and10B for cabin windows is shown here. If the fuselage cell of aircraft100 is deformed elastically by flight movements, several strip-shapedindependent systems, for example panel 1, 1′, 1″ or cell arrays 20A,20A′, 20A″ are provided. Combinations thereof can however also beconnected into a system. By means of an arrangement of several panels 1,1′, 1″ and further cell arrays 20B, 20B′, 20B″, 20C, 20C′, 20C″, a highdegree of redundancy is additionally achieved, i.e. the failure ofindividual modules does not impair the function of the overall system,but rather has only a slight effect on the maximum achievable power.

The connection elements between panel 1 or cell array 20 to themedia-carrying lines can, in the function as a shut-off device 24, bedesigned as gas-tight rapid-action couplings and serve at the same timeas a mechanical bearing element.

In a further embodiment (not shown), the coupling elements of themedia-carrying lines, but in particular in combustion-gas line 18, maycontain safety valves, which with a sudden pressure drop immediatelyclose the supply and discharge lines for affected panel 1, 1′, 1″ orcell array 20, 20′, 20″.

It can further be seen in FIG. 3 that the condensate carried away frompanels 1, 1′, 1″ or cell arrays 20, 20′, 20″ via water line 17 can betaken up in a water collection tank 25 and used for water supply 23 forthe passenger cabin. For the provision of air supply 15 to the fuelcells, cabin air 27 for example is used and conveyed by means of acompressor 26 to air supply 15.

FIG. 4 shows, in a sectional representation, a fuel-cell panel 1 in theinstalled state in the area of outer skin 10 of the aircraft. Theinstallation of panel 1 takes place close to fuselage skin 10 betweenstringer 12 and interior cabin lining 8, whereby the width of panel 1can be adapted to the spacing of ribs 11 of aircraft 100.

Single-cell or few-cell fuel cells are provided for panel 1, cathodeside 5 of said cells forming a chamber which points towards cold outerside 14 of aircraft 100 in order to achieve here the condensation of thewater contained in the exit air, and anode side 3 of said cells beingbounded by a chamber carrying combustion gas (e.g. hydrogen).

Energy-tapping of direct current takes place at pole-plate cathode 6 andat pole-plate anode 4 respectively.

The water obtained through condensation forms drops on the cathode-sidecolder wall of chamber 5 facing fuselage skin 10, whereby the drops rundown thereon following the force of gravity and are collected there in acollection pipe 17 and transported in the direction of a collectioncontainer 25. An air stream introduced from above is provided for thecathode-side cell supply with oxygen and also serves for the transportof water.

The cathode space is bounded by a housing, which outer side can beheated. This heating is designed in such a way that a temperature can beselected in order to use the outer wall of cathode space 5 at the sametime as a condensation area for the water vapour arising in the fuelcell process.

This water collects at the bottom of cathode space 5 and is drawn off,via line system 17 (see FIG. 3) which connects all panels 1, 1′, 1″together, by means of a pressure difference between cathode space 5 andconnected line system 17. The supply with air takes place via secondpiping system 15 (see FIG. 3), which is located above panels 1, 1′, 1″.

The heating of the cathode-space outer wall takes place via a system ofheat carriers or heat conductors 7, which are able to transport the heatarising at anode side 3 onto cathode side 5 lying opposite. This cantake place by means of liquid, gaseous or solid media, for example bymeans of standard conductors, such as copper. The heat loss on anodeside 3 lying on the inside, i.e. pointing towards the cabin, is herebyadjusted in such a way that optimum heat conditions are established forpassenger comfort. The heat arising on anode side 3 is thus used on theone hand to heat the cathode side in order to prevent freezing of thewater arising here and, at the same time, to deliver heat to passengercabin 13 when required.

The anode space is also arranged in a housing. The combustion gas (H₂)is admitted from below into the anode space. Excess quantities are drawnoff at the panel upper side and brought back into the H₂ storage unit.

For safety reasons, wall 8 on the cabin side is secured by an internalreinforcement against penetration of objects.

The anode-side chamber, i.e. the chamber carrying combustion gas (H₂),points towards the inside or cabin side of the aircraft.

The arrangement may allow that, even in the event of damage to outerskin 10 with perforation into the cabin, only small quantities ofcombustion gas can flow out. The special arrangement and the pressureconditions between cabin 13 and external-air side 14 additionallyprevent combustion gas being able to flow into the cabin interior, butrather it always flows in the direction of the external perforation andis thus released into the open atmosphere.

In this event, furthermore, the gas flowing to affected fuel-cell panel1, 1′, 1″ is switched off immediately by safety valves, so that onlyvery small gas quantities can escape. The discharging water-collectionline of affected panel 1, 1′, 1″ is also closed, so that the remainingpanels present are able to continue generating water and sending it intothe water circuit.

In the event of the penetration of an object through outer skin 10 ofthe aircraft and panel 1, 1′, 1″, the following situation arises:

During flight, a pressure difference of approx. 0.5 bar (pressuredifference=0 on the ground) arises between the external pressure and thecabin pressure. The combustion gas is present in panel 1, 1′, 1″ with apressure of approx. 1.2 bar, which means a pressure difference ofapprox. 0.7 bar to external-air side 14. It follows from this that, inthe event of a perforation, the gases present in the panel flow throughthe perforation opening outwards, i.e. in the direction of external-airside 14.

On the ground, with equalized pressure conditions, this situation willnot occur. Here, the curved shape of panel 1, 1′, 1″ and its position inthe upper area of the cabin assists the outflow of the gases toexternal-air side 14.

In addition, each fuel-cell panel is automatically cut off from thecombustion-gas supply by the safety valve when there is a loss ofpressure. This guarantees that only the combustion gas present infuel-cell panel 1, 1′, 1″ at the time of the perforation can flow out,which however does not form an inflammable mixture inside cabin 13 onaccount of the quantitative proportions.

A mechanical protection against perforation at the wall of fuel-cellpanel 1, 1′, 1″ pointing towards cabin side 13, for example made of acarbon fibre mesh, largely prevents this situation from arising at all.Such carbon fibre mesh is at the same time suitable for forming themechanical structure of panel 1, 1′, 1″ and the reinforcement points forthe attachment to the aircraft structure.

The functional sequence for the generation of water is described in thefollowing:

Supply of Fuel and Air

Hydrogen H₂ is provided as the fuel. This can be carried on board ingaseous or liquid form or can be reformed in a reformer 201 from ahydrocarbon—in the present case from kerosene. In the case of thereformation of hydrogen from kerosene, attention should be paid to thesulphur fraction contained in the kerosene. If need be, adesulphurisation process is connected upstream of the reformer 201. Inaddition, a CO shift stage is connected downstream of the reformer, saidCO shift stage converting carbon monoxide arising in the reformation,which is harmful to the fuel cell, into carbon dioxide which is harmlessto the fuel cell.

As an alternative to a reformer with the shift stage anddesulphurisation unit, a high-temperature fuel cell can perform the samefunction. In the present case, the latter is operated in such a way thatit reforms much more hydrogen from kerosene than it itself requires forthe generation of electrical energy through an applied electrical load.This excess of hydrogen is separated from the other exit gases by meansof a molecular sieve, cooled and fed to the panel fuel cells.

The supplied gases (air and H₂) are preheated to the optimum operatingtemperature of the fuel cells. This can be achieved by means of the heatarising in the reformer process. An electric preheater could also beused.

Condensation

In order to guarantee that the cathode condensate does not freeze atgreat flight altitudes with external temperatures well below thefreezing point of water (for example −55° C.), the cathode-side externalchamber wall contains a device for temperature regulation, which enablesa uniform temperature distribution on this wall as narrowly above thefreezing point of water as possible, in order in this way to obtain thegreatest possible quantity of condensate.

The temperature regulation can be carried out for example by couplingtemperature sensors to an adjustable heat release—for example throughPelletier elements—on anode side 3 into heat conductor 7. At the sametime, a cooling device—for example supplied by the air-conditioning unitor by Pelletier elements—acts on this wall during the ground operationin a warmer environment or in the presence of solar radiation on theouter skin, in order that condensate can be obtained under all operatingconditions.

Drawing off of Water and Distribution

Conduit 17 for the collection of the cathode-side condensate (H₂O) runsbeneath fuel-cell panels 1, 1′, 1″, each of panels 1, 1′, 1″ beingconnected to said conduit. This collection line leads to a watercollection container 25.

In order to allow a complete draining of the condensate from fuel-cellpanels 1, 1′, 1″, collection container 25 is pressurised with the cabinpressure in one form of embodiment, whilst the air being supplied topanels 1, 1′, 1″ has a slight overpressure produced by compressor 26(see FIG. 3) (for example approx. 0.7 bar cabin pressure to approx. 1.2bar compressor pressure). The pressure difference thus arising betweenpanel 1 (or cell array 20) and collection container 25 causes theoccurring condensate to be drawn off from fuel-cell panel 1 in thedirection of collection container 25.

Compressor 26 for the air supply to fuel-cell panels 1 draws off air 27from the cabin, so that overall the pressure equilibrium in the cabinremains intact.

1. A method for generating water on board an aircraft comprising thesteps of: providing at least one fuel cell having a cathode side with afirst chamber arranged towards an outside of the aircraft; forming atleast one of a fuel-cell panel and a cell array, which includes the atleast one fuel cell, such that the at least one of the fuel-cell paneland a cell array is curved and arranged in close proximity to a fuselageskin of the aircraft; supplying cold air from an external-air side ofthe aircraft to the cathode side of the at least one fuel cell; in thefirst chamber, condensing the cold air supplied to the at least onefuel-cell to form water; and collecting the water for consumption. 2.The method according to claim 1, wherein the at least one fuel cell hasan anode side, wherein a combustion gas is fed to the anode side of theat least one fuel cell, and wherein a waste heat arising in the at leastone fuel-cell on the anode side is used partially to supply heat to atemperature control process between chambers of the at least one fuelcell and an outer wall to form a condensate and partially to supply heatinto an aircraft cabin.
 3. The method according to claim 1, furthercomprising the steps of: actively heating the cathode side of the atleast one fuel cell; and simultaneously cooling an anode side of the atleast one fuel cell, wherein the active heating and simultaneous coolingare performed by heating and cooling elements.
 4. The method accordingto claim 1, further comprising the steps of: providing a pressuredifference between an air supply and a condensate discharge fortransporting the condensate from the fuel cell in the direction of acollection container.
 5. The method according to claim 1, furthercomprising providing hydrogen for the operation of the at least one fuelcell, the hydrogen being obtained in a reformer process from ahydrocarbon, and the hydrogen containing fractions of carbon dioxide butno carbon monoxide.
 6. The method according to claim 5, wherein the atleast one fuel cell is a high temperature fuel cell, the reformerprocess taking place in the high-temperature fuel cell, and the fuelcell being adjusted in terms of its operating parameters such that itproduces free H₂ molecules form the hydrocarbon and water and convertsreleased carbon monoxide fractions into carbon dioxide.
 7. The methodaccording to claim 1, wherein a plurality of fuel cells is provided; andwherein a flexible adaption to an instantaneous current consumption isperformed by an electrical connection of the plurality of fuel cells.